1. Field of the Invention
The present invention relates to an image forming apparatus using an electrophotographic method or an electrostatic recording method, particularly, an image forming apparatus such as a copying machine, printer, facsimile (FAX), and multifunction peripheral including a plurality of these functions.
2. Description of the Related Art
A conventional image forming apparatus such as a copying machine and printer using an electrophotographic method forms a patch image on a photosensitive member, and corrects image forming condition of an image forming process device based on a result of detected density of the patch image.
For example, an apparatus discussed in Japanese Patent Application Laid-Open No. 2005-316064 includes, in order to correct an image forming condition of an image forming process device, an image density sensor of an optical type at a position facing a photosensitive member.
Further, Japanese Patent Application Laid-Open No. 2005-316064 employs a configuration in which a detection window of the image density sensor is closed with a shutter when detection is not performed to prevent scattered toner from contaminating the image density sensor.
However, when the shutter is provided in the image forming apparatus, a new problem arises that the scattered toner adheres to an outer surface of the shutter.
If a large amount of toner adheres to the shutter, when the density of the patch image is detected during a job for continuously forming a plurality of images, the toner may be scattered from the shutter when the shutter is opened and closed, and adhere to a primary image.
In other words, every time the shutter is opened and closed to detect the density of the patch image, the toner scattered from the shutter may generate a fault in an image.